Apparatus for measuring tensile properties of hair

ABSTRACT

A strand of hair is clamped between two posts, both of which are movably supported on a base. The first post is urged in one direction by a spring. Initially the spring and associated post are latched in position with the spring compressed. The second post remains unloaded between two compression springs. To make a measurement, the latch is released and the first post permitted to move away from the second post under urging of the spring. The rate of movement of the post is limited by a dash-pot device. As the first post moves away, the force of the pull of the hair is transferred to the second post. This force is detected by an electronic sensor. The extent of movement between the two posts is also detected electronically providing a measure of the elongation of the hair. Both readings are recorded on dials.

United States Patent [191 Yates 5] Nov. 25, 1975 APPARATUS FOR MEASURINGTENSILE PROPERTIES OF HAIR Primary Examiner-James J. Gill Attorney,Agent, or FirmChristie, Parker & Hale [57] ABSTRACT A strand of hair isclamped between two posts, both of which are movably supported on abase. The first post is urged in one direction by a spring. Initiallythe spring and associated post are latched in position with the springcompressed. The second post remains unloaded between two compressionsprings. To make a measurement, the latch is released and the first postpermitted to move away from the second post under urging of the spring.The rate of movement of the post is limited by a dash-pot device. As thefirst post moves away, the force of the pull of the hair is transferredto the second post. This force is detected by an electronic sensor. Theextent of movement between the two posts is also detected electronicallyproviding a measure of the elongation of the hair. Both readings arerecorded on dials.

3 Claims, 5 Drawing Figures U.S. Patant N0v.25, 1975 Sheet20f3 3,921,443

U.S. Patent N0v.25, 1975 Sheet30f3 3,921,443

. APPARATUS FOR MEASURING TENSILE PROPERTIES OF HAIR BACKGROUND OF THEINVENTION the elongation and tensile strength of a single hair strand.

It has long been recognized in the care and treatment of hair that oneof the clues to the health and vitality of the hair is its strength andelasticity as measured by the extent the hair stretches or elongatesbefore breaking. For example, a weak tensile strength indicates abreakdown of the cross linkages which unite the keratin proteinmolecules and/or an excessive loss of the protein molecules themselves.Such a. condition might be caused, for example, bysubjecting the hair toharsh alkaline chemicals or excessive exposure to the suns ultravioletrays. A high tensile strength, on the other hand, indicates a sufficientprotein structure with many cross linkages uniting the entire molecularstructure of the hair.

While the elasticity of the hair also is related to the unity of thisprotein structure, it is more directly related to the water moleculeswhich are present to a greater or lesser extent in the hair structure.The water molecules soften the attraction between keratin proteinmolecules, and when present in the proper amount allow the hair tostretch to 175% normal elongation before breaking. Excessive watermolecules in the hair allow the hair to stretch beyond the normallimits. If the hairs moisture is removed, the hair becomes brittle andlacks the proper elongation.

While devices have heretofore been proposed which purport to measure thestrength and elongation of hair, such known devices have been lacking inaccuracy and reproducibility of results, particularly in the hands ofinexperienced operators, or have been too complex and expensive to be'sold and used in great numbers.

SUMMARY OF THE INVENTION The present invention is directed to apparatusfor simultaneously measuring both the strength and elongation of humanhair. The apparatus is designed to operate in a manner whichsubstantially eliminates the human element of the operator in obtainingconsistently accurate and reproducible results. This is accomplished inbrief by providing apparatus in which hair is clamped around two posts.One of the posts is moved away from the other post at a substantiallyconstant velocity, transferring a force to the other post throughtension in the hair strand. This force is resisted by a spring. Anelectronic sensor measures the displacement of the spring-loaded postrelative to a fixed reference and equates this distance for forcingexerted bythe hair. A second sensor electronically measures thedisplacement of the constantly moving post relative to the other post,which indicates the elongation of the hair. An electronic processorinterprets the data from the sensors, and displays the'data on twometers.

DESCRIPTION OF THE DRAWINGS For a more complete understanding of theinvention, reference should be made to the accompanying drawings,wherein:

FIG. 1 is a perspective view of the instrument of the present invention;1

FIG. 2 is a plan view of the instrument with the cover removed; 7

FIG. 3 is a sectional view taken substantially on the line 3--3 of FIG.2;

FIG. 4 is a perspective view of the molded diaphragm used in thehydraulic damping system; and

FIG. 5 is a schematic wiring diagram of the electronic measuringcircuit.

DETAILED DESCRIPTION Referring to the drawings in detail, the numeral 10indicates generally a hair measurement apparatus hav-' ing a cover 12and a base 14. The cover is preferably formed with a slanting front onwhich are mounted a pair of meters 16 and 18 which are calibrated toindicate respectively elongation, in suitable units of length, andstrength in suitable units of force. Projecting out of the front of thecover are a pair of relatively movable binding posts 20 and 22. Thebinding posts 20 and 22. The binding post 20 is provided with a V-shapedgroove 24 extending around the periphery thereof. The

binding post 22 is provided with an outer flange 26 and a shaft 28 onwhich is threaded a rotatable clamping member 30. Rotation of theclamping member 30 by a radially projecting knob 32 causes the clampingmember 30 to move axially of the shaft 28, bringing a clamping surface34 into clamping relationship with the inside surface of the flange 26..A pin 36 limits the rotation of the clamping member 30. In operation ofthe apparatus, a single strand of hair is formed in a loop. The bightportion of the loop is positioned in the groove 24 with the two ends ofthe loop extending over the shaft 28 where they are clamped between theclamping surface 34 of the clamping member 30 and the inside of theflange 26.

In addition to the meters 16 and 18, the slanting front panel of theinstrument also includes a knob of an Onl- Off control switch 38, whichis turned on to activate the measurement circuit as hereinafterdescribed. Also, there is provided a Start control knob 39. When movedto the start position, the knob 39 initiates movement of the bindingpost 22 to the right, as viewed in FIG. 1, causing the loop of hairunder test to be brought into tension around the binding post 20 andtending to pull the binding post 20 to the right also'. As hereinafterdescribed, as the binding post 20 is pulled to the right by the strandof hair, it resists the movement with increasing force, thus causing thehair to be placed under increasing tension as the binding post 22continues to move to the right, until the tension on the hair exceedsthe breaking point and the hair loop snaps, thereby releasing thebinding post 20 to return to its initial position.

Referring to FIGS. 2 and 3, the numeral 40 indicates a shaft which isjournaled in supporting blocks 42 and 44, the supporting blocks beingrigidly mounted on the base 14. Block 42 is clamped to the base by meansof screws 46 and 48 extending through elongated slots in the block 42,the slots extending parallel to the longitudinal-axis of the shaft 40.Thus the supporting block 42 is adjustable relative to the base 14 byloosening the screws 46 and 48. The shaft 40 passes through a thirdblock 50 also mounted on the base 14.

A first slider assembly, indicated generallyat 52, is slidably mountedon the shaft 40 by means of a ball bearing type sleeve 54. The sleeve 54permits the slider assembly 52, to move freely along the shaft 40 withvery low frictional resistance. The binding post is anchored .to theslider assembly 52 and is laterally movable therewith along the shaft40. The slider assembly 52 is prevented from rotating about the axis ofthe shaft by means of a ball bearing roller 58 which runs in a slot 59in the block 50.

The null position of the binding post 20 and associated slider assembly52 is determined by a pair of compression coil springs 62 and 64 whichare positioned concentrically on the shaft 40 in either side of theslide assemblyfThe spring 62 is held in a counterbore 66 in thesupporting block 42. Similarly the spring 64 is seated in a counterbore68 in the intermediate block and in a counterbore 70 in the first sliderassembly 52. Adjustment of the supporting block 42 to the right or leftpermits the null position of the binding post 20 to be shifted whilestill maintaining a zero net force on the slider assembly 52longitudinally of the shaft 40.

The binding post 22 and associated hair clamping mechanism is mounted ona slider block 72. The block 72 has a hole which receives the shaft 40,the block being fixedly secured to the shaft 40, for example, byclamping set screws 74. The block 72 has the portion 76 extendingparallel to the shaft and extending beyond the block 50 toward the slideassembly 52. The binding post 22 is mounted on the portion 76 in closeproximity to the post 20 when in the initial or starting position. Acompression spring 78 concentric with the shaft 40 and extending betweenthe fixed block 50 and the slider block 72 urges the block 72 to theright together with the shaft 40. The block 72 is held in the initialposition against the force of the spring 78 by a release lever 80 whichis pivotally supported on the block 44 for horizontal movement about anaxis 82. A roller 84 normally engages the block 72 under the urging of atension spring 86 extending between the lever 80 and block 44. The Startknob 39 which projects out to the top of the cover, as described inconnection with FIG. 1, is attached to the lever 80, permitting thelever 80 to be moved away from the block 72, thereby moving the stoproller 84 out of contact with the block 72. The block 72 is then urgedto the right by the compression spring 78.

The rate of movement of the block 72 with its binding post 22 is limitedby a dash-pot assembly mounted in the block 44. The dash-pot assemblyincludes two cylindrical openings 88 and 89. The opening 88 extends inaxial alignment with the shaft 40, one end of the shaft 40 extendinginto the opening 88. The second opening 89 is substantially larger indiameter than the opening 88 and includes a piston 90 and compressionspring 92 therein. A single molded flexible rubber diaphragm has a baseportion 94 and two cylindrical shaped bubble portions 96 and 98 having adiameter corresponding respectively to the openings 88 and 89. Thebubble portions are inserted in the openings and the base 94 is clampedin place by a plate 100. The two bubble portions of the diaphragm areconnected by a hollow ridge portion 102 which forms a passage connectingthe interior of the two bubble portions when the base 94 is clamped inposition by the plate 100.

It will be seen that in operation the dash-pot assembly operates toresist the movement of the shaft 40. As the shaft 40 moved to the right,as viewed in FIG. 2, it forces hydraulic fluid within the bubble 96 outthrough the passage 102 into the bubble 98. A set screw 106 extendingthrough the plate opposite the passage 102 4 can be adjusted to adjustthe rate of flow at which fluid passes between the two bubbles, therebycontrolling the rate at which the shaft 40 moves the binding post 22under the urging of spring 78.

Strength and elongation measurements are performed by the electroniccircuit shown in FIG. 5. The circuit is controlled by two sensors, whichpreferably are in the form of linear otentiometers. A strength measuringsensor, indicated generally at 110, is mounted on the base 14 and has amovable plunger 1 12 connected to the slider assembly 52 by a pin 114,as shown in FIG. 2. An elongation sensor, indicated generally at 115, ismounted on the slider assembly 52. The sensor has a movable plunger 116which extends through an opening in a lug 118 on top of the slider block72. The plunger 116 is secured to the block by a pin 120.

As the binding post 20 is moved from its null position by the movementof the binding post 22 through the strand of hair looping the post 20,the sliding contact of the sensor is moved proportionately. As the hairin the loop elongates under tension, the slider block 72 moves away fromthe slider assembly 52. As a result the sliding contact of the sensormove in direct proportion to the elongation of the hair strand.

Referring to the circuit diagram of FIG. 5, the sensor 110 is connectedacross a positive potential source. The moving contact 112 of the sensoris connected through a resistor 122 to the base of an NPN transistor 124connected as an emitter follower across a potential source. The emitterload is a capacitor 126. The milliammeter 18 is controlled in responseto the voltage across the capacitor 126 through two transistor stages128 and 130. The meter 18 is calibrated in grams or other suitable unitsof force. As greater and greater force is applied through tension in thehair fiber to the post 20, the change in the position of the contact1120f the sensor 110 is reflected in a correspondingincrease in currentthrough the meter 18.

When the tension on the hair strand under test reaches the breakingpoint, the voltage on the output of the potentiometer wiper contact 112drops back to substantially zero. However, the capacitor 126 retains itscharge, holding the meter 18 at the reading corresponding to the forcerequired to break the hair.

Similarly, the elongation sensor 115 has the wiper contact 116 connectedthrough a series resistor 132 to the base of a transistor 134 connectedas an emitter follower, with a capacitor 136 as the emitter load. Themilliammeter 16 is controlled from the voltage across the capacitor 136through a pair of transistors 138 and 140.

In order to derive a measurement of the elongation of the hair at thetime the hair breaks, an interlock circuit is provided which turns offthe transistor 134 when the sensor 110 drops back to its null positionat the time the hair strand snaps. To this end, an NPN transistor 142 isconnected with the collector and emitter circuit in shunt between thebase of the transistor 134 and ground. The NPN transistor 142 isnormally turned off, but when turned on acts to turn off the transistor134, thereby holding the meter 16 at the level determined by theexisting charge on the capacitor 136. The transistor 142 is controlledby a transistor 144 having its base connected to the wiper contact 112of the sensor 110. The emitter is connected to ground through acapacitor 146 while the collector is connected through a resistor 148 tothe base of a PNP transistor 150. The collector of the transistor 150 isconnected through a resistor 152 to the base of a transistor 154, havinga collector load resistor 156. The base of the transistor 142 is in turnconnected to the collector of the transistor 154. Normally thetransistor 144 is conducting as are the transistors 150 and 154, causingthe transistor 142 to be biased off. However, a transistor 158 havingits base connected also to the wiper contact 112 is connected as anemitter follower, having the capacitor 146 as the emitter load.

When the hair strand breaks, the wiper contact 112 drops back to itsinitial position, causing the transistor 144 to be turned off, which inturn causes the transistors 150 and 154 to be turned off and thetransistor 142 to be turned on. This turn off the transistor 134,causing the meter 16 to be held at the level set by the charge on thecapacitor 136.

More reliable hair strength measurements are obtained if the tensionforce is measured at a level less than the maximum elongation of thehair at the breaking point. For this reason, a transistor 160 isprovided having its collector-emitter circuit connecting the base of thetransistor 124 to ground. The base of the transistor 160 is connectedthrough a resistor 162 to the emitter of the transistor 140. By thisarrangement, the transistor 160 is initially biased off, allowing thecapacitor 126 to charge to the potential of the wiper contact 1 12. Atsome predetermined amount of elongation, preferably of the order of topercent, the voltage across the resistor 164 reaches a level sufficientto turn on the transistor 160, thereby preventing further charging ofthe capacitor 126. The meter is held at the reading level correspondingto the predetermined amount of elongation. The meters 16 and 18 arereset to zero by the switch 38 being turned off.

Thus it will be seen that a measurement device is provided whichindicates tensile strength and elongation of hair. By increasing thetension on the hair at a fixed rate, highly reproducible results areobtained. At the same time, the device is very simple and fool-proof inits operation.

What is claimed is:

1. Apparatus for measuring the tensile properties of hair or otherfibers, comprising:

a base member,

a movable first hair engaging member,

means supported on the base for guiding said first member along a linearpath,

a movable second hair engaging member spaced from the first member;

the hair under test extending between the first and second members,

means supported on the base for guiding said second member along alinear path parallel to the path of movement of the first member,

6 first spring means extending between the first member and the base forresisting movement of the first member with increasing force withdisplacement of the first member in the direction of the second member,means including second spring means extending between the second memberand the base for moving the second member in the opposite direction atsubstantially constant velocity to put the hair under uniformlyincreasing tension against the urging of the first member by the firstspring means, first indicating means for indicating changes in positionof the first member relative to the base, second indicating means forindicating changes in position of the second member relative to thefirst member and a third spring means extending between the first memberand the base for urging the first member in the opposite direction thanthat of the first spring means to provide an adjustable null position ofthe first member. 2. Apparatus for measuring the tensile properties ofhair or other fibers, comprising:

a base member, a movable first hair engaging member, means supported onthe base for guiding said first member along a linear path, a movablesecond hair engaging member spaced from the first member; the hair undertest extending between the first and second members, means supported onthe base for guiding said second member along a linear path parallel tothe path of movement of the first member, first spring means extendingbetween the first member and the base for resisting movement of thefirst member with increasing force with displacement of the first memberin the direction of the second 7 member, means for moving the secondmember in the opposite direction at substantially constant velocity toput the hair under uniformily increasing tension against the urging ofthe first member by the first spring means, first indicating means forindicating changes in position of the first member relative to the base,second indicating means for indicating changes in position of the secondmember relative to the first member, and means responsive to said secondindicating means for locking the first indicating means when said secondindicating means indicates a predetermined change in position of thesecond member. 3. Apparatus of claim 1 further including meansresponsive to the first indicating means for locking the secondindicating means when the first member drops back to its initialposition on breaking of the hair.

1. Apparatus for measuring the tensile properties of hair or otherfibers, comprising: a base member, a movable first hair engaging member,means supported on the base for guiding said first member along a linearpath, a movable second hair engaging member spaced from the firstmember; the hair under test extending between the first and secondmembers, means supported on the base for guiding said second memberalong a linear path parallel to the path of movement of the firstmember, first spring means extending between the first member and thebase for resisting movement of the first member with increasing forcewith displacement of the first member in the direction of the secondmember, means including second spring means extending between the secondmember and the base for moving the second member in the oppositedirection at substantially constant velocity to put the hair underuniformly increasing tension against the urging of the first member bythe first spring means, first indicating means for indicating changes inposition of the first member relative to the base, second indicatingmeans for indicating changes in position of the second member relativeto the first member , and a third spring means extending between thefirst member and the base for urging the first member in the oppositedirection than that of the first spring means to provide an adjustablenull position of the first member.
 2. Apparatus for measuring thetensile properties of hair or other fibers, comprising: a base member, amovable first hair engaging member, means supported on the base forguiding said first member along a linear path, a movable second hairengaging member spaced from the first member; the hair under testextending between the first and second members, means supported on thebase for guiding said second member along a linear path parallel to thepath of movement of the first member, first spring means extendingbetween the first member and the base for resisting movement of thefirst member with increasing force with displacement of the first memberin the direction of the second member, means for moving the secondmember in the opposite direction at substantially constant velocity toput the hair under uniformily increasing tension against the urging ofthe first member by the first spring means, first indicating means forindicating changes in position of the first member relative to the base,second indicating means for indicating changes in position of the secondmember relative to the first member, and means responsive to said secondindicating means for locking the first indicating means when said secondindicating means indicates a predetermined change in position of thesecond member.
 3. ApparAtus of claim 1 further including meansresponsive to the first indicating means for locking the secondindicating means when the first member drops back to its initialposition on breaking of the hair.